#define _CRT_SECURE_NO_WARNINGS
class Solution {
public:
    bool containsNearbyDuplicate(vector<int>& nums, int k) {
        unordered_map<int, int> hash;
        for (int i = 0; i < nums.size(); i++)
        {
            if (hash.count(nums[i]))
            {
                if (abs(i - hash[nums[i]]) <= k) return true;
            }
            hash[nums[i]] = i;
        }
        return false;

    }
};